I'm probably the only one who deals with this issue, but my primary hard drive (C) has only 25 GB of memory and is filled to the brim. I would love the use some new Dune soundbanks but the default folder is in C/users/documents/synapse audio/... and I cannot afford to take in another 500mb+ on my primary hard drive. Is there anyway that I can change the default preset folder to my secondary (D) drive which has plenty of space?

No. Everything is pretty much hard-coded to store in your Documents folder.

But you could move your entire documents folder (and Sypanse Audio folder with it) to another partition/drive.

Right click on your Documents folder from Explorer -> Properties -> Location -> Move button... and then just select a different location and confirm that you want to move all of its content.With that, you will secure that you'll pretty much never lose your Documents folder AND you'll free some space on your C drive.